Physical servers in a network may be located in a rack unit that houses a plurality of network devices. The physical servers may connect to a top of rack (ToR) switch that is configured to route communications between the physical servers in the rack unit and other network elements. The physical servers may host one or more virtual switches and virtual machines. The virtual switches may be configured to manage communications of virtual machines in particular virtual networks or subnets. Virtual machines may be segmented into particular virtual networks or subnets via control protocol messages exchanged between the virtual switch of a physical server and the ToR switch that manages the physical server. An example control protocol for provisioning the virtual machines is the Virtual Station Interface (VSI) Discovery Protocol (VDP) as defined by the Institute of Electrical and Electronic Engineers (IEEE) 802.1Qbg standard.